This invention relates to improvements in microscopes, and particularly to a microscope accessory which will permit measurement of radiation transmitted through a sample after reflection from a surface located on the side of the sample away from the objective lens.
As explained in common assignee/common inventor application Ser. No. 921,212, filed Oct. 20, 1986, it is highly advantageous to use reflectance microscopy in situations in which detector-received radiation is modulated by transmission through the sample. This use of the reflectance mode for transmission measurements conserves space in the microscope, and permits a single objective lens to transmit both pre-sample and post-sample radiation.
Another microscope improvement set forth in common assignee/common inventor application Ser. No. 921,066, filed Oct. 20, 1986, discloses the advantages of a "projected field stop" which provides a feature sometimes referred to a "redundant aperturing". This feature, which can be more accurately labeled "diffraction filtering" or "matched field illumination (MFI)", reduces diffraction effects in the microscope, and thus improves spatial resolution, by causing both pre-sample and post-sample radiation to pass through area-limiting field stops. The MFI effect provides definite benefits, particularly when it is necessary to distinguish between adjacent microscopic samples of two different materials.
Yet another microscope improvement set forth in common assignee/common inventor application Ser. No. 907,995, filed Sept. 16, 1986, discloses the advantages of high radiation throughput obtained in the microscope reflectance mode by using an "injection" mirror, which causes substantially 50% of the available IR beam to reach the detector.